Synthesis and thermoelectric properties of Bi-doped SnSe thin films

Bi doped n-type SnSe thin films were prepared by chemical vapor deposition (CVD) and their structure and thermoelectric properties were studied. The x-ray diffraction patterns, x-ray photoelectron spectroscopy, and microscopic images show that the prepared SnSe thin films were composed of pure SnSe crystals. The Seebeck coefficients of the Bi-doped SnSe were greatly improved compared to that of undoped SnSe thin films. Specifically, Sn_0.99Bi_0.01Se thin film exhibited a Seebeck coefficient of -905.8μV·K^-1 at 600 K, much higher than 285.5 μV·K^-1 of undoped SnSe thin film. Further first-principles calculations reveal that the enhancement of the thermoelectric properties can be explained mainly by the Fermi level lifting and the carrier pockets increasing near the Fermi level due to Bi doping in the SnSe samples. Our results suggest the potentials of the Bi-doped SnSe thin films in thermoelectric applications.     

单光束楔形镜云纹干涉法

本文利用单光束楔形镜云纹干涉法代替传统的双光束云纹干涉法进行位移场和应变场的测量.单光束云纹干涉法具有光路简单,不受环境干扰等特点.本文将云纹干涉法的波前理论与近代光学信息技术有机地结合起来,对单光束干涉系统进行了分析,得到了记录的光强和再现的位移应变公式.利用该系统,得到了三点弯矩形梁的全场位移条纹图和应变条纹图.     

Entangled States Used in Remote Information Concentration and Their Properties

We analyse a process of remote information concentration achieved by the W state. The result turns out to be neither as good as performed by the GHZ state nor as by the Smolin bound entangled state. Based on this particular phenomenon, the properties of the three entangled states are realized.     

建构主义理论在中学数学课堂教学中的应用

行为主义教学观强调“刺激一反应”理论,全面实施素质教育,学生不可能通过大量的反复操练去达到系统掌握知识的目的,尤其是在知识爆炸和信息多渠道获取的今天,要求学生去穷尽所有数学知识也就勉为其难.因而不从根本上改变我们的教学理念和教学方式,就会陷于教师教得苦,学生学得累的尴尬局面.笔者尝试在建构主义理论指导下,试图将每一节数学课变成建构学生新的数学知识的主阵地.     

能同时产生不同频率脉冲信号的双波长主动锁模光纤激光器

用两只光纤光栅（FBG）作波长选择器件，实现了一种能同时输出两个不同重复频率的光脉冲序列的双波长主动锁模环形腔光纤激光器。通过调速外加调制信号的频率，使其中一个波长工作在谐波锁模状态，另一个波长工作在有理数谐波锁模状态，实验在2GHz和2.5GHz的调制频率下都成功地获得了双波长且重复频率不同的光脉冲序列，脉冲宽度分别约为60ps和45ps。     

A Novel Bi-wavelength Method for Accurately Measuring Gain and Noise Characteristics of an Erbium-Doped Fibre Amplifier for Multi-Channel Wavelength Division Multiplexing Transmission

Gain and noise figure (NF) are the most important two parameters of an erbium-doped fibre amplifier (EDFA) for a multi-channel wavelength division multiplexing (WDM) transmission system. A simple bi-wavelength method for accurate gain and NF spectrum measurement of EDFA for WDM applications is proposed. A saturating input signal, whose power equals to the sum of all the WDM signal power and whose wavelength is determined by the channel numbers and the wavelength of the WDM input signals, saturates the EDFA in a degree as the same as the WDM signals input. Meanwhile, a small power probe signal scans and measures the gain and the NF value at every wavelength of the WDM input signals. Investigative results by numerical simulation show that the gain and the NF spectra measured by this method have good agreement with the real spectra of the WDM signal input in a large total input power range. The maximum errors of the gain and the NF are less than 0.2 dB and 0.16dB, respectively, for a 50-channel input case. The method is competent for the accurate gain and the NF spectrum measurement of the fibre preamplifier and the line-amplifier for WDM applications and has the advantages of simplicity, convenience and easy implement.     

带有控制约束的不确定非线性系统的H_∞控制

研究了一类含有控制约束(饱和执行器)的不确定非线性系统的H_∞最优控制问题.首先,引入非二次型函数来解决控制受限的问题.然后借助二人零和微分对策理论研究H_∞最优控制问题,提出了模型自由的在线学习算法,仅仅通过在线获得的系统的状态信息而无需模型知识就能很好的解决H_∞控制问题.建立了执行网-评价网-扰动网三网络结构完成算法的在线实现.最后,利用李雅普诺夫(Lyapunov)稳定性理论给出了系统的稳定性分析,仿真算例验证了算法的有效性.     

面向智能变电站的信息流可靠性分析模型

智能变电站是智能电网可靠运行的关键环节和重要基础,为避免变电站可靠性的单一定性评估方法给变电站状态监测、检修决策带来的不足,在分析智能变电站及其信息流特征的基础上,从不同角度归纳了智能变电站网络可靠性的评估方法。给出一种基于信息流传输时延、丢包率和各信息流QoS要求的信息流可靠性评估模型,并通过在稳态和极限流量运行方式下对该模型进行了仿真实验,结果表明该方法能在一定程度上定量评估智能变电站信息流的可靠性问题。     

DNA小沟结合二脒:水分子的识别作用

采用分子动力学模拟了DB921-DNA复合物, 通过7 ns的模拟研究表明: DB921一端的氨基氮原子与一个水分子形成氢键, 同时, 水分子又与DNA的5位A碱基的氮原子形成一个氢键. 水分子在DB921与DNA小沟结合中起了桥连的作用, 使得直线型的芳香二脒化合物DB921通过水桥与DNA小沟结合, 水分子诱导DB921分子与DNA的小沟域构型相适应, 与DNA小沟域的AATTC碱基有较强的结合作用. 在分子水平上提供了DB921与双螺旋DNA相互作用的结构及复合物的动态变化情况, 指出水分子在DNA小沟结合二脒化合物中的识别作用, 为设计出更高生物活性的DNA小沟结合剂提供一定的理论依据.